The following is a mitigation framework for the encounter.
It is not a plan for every single cooldown available to the party; instead, think of the following as a bare-bones framework to work with- i.e: these are the things that people will generally look for when mitigation is missing.
Rampart should be used towards the end of the castbar, as we want it to cover Burn Mark as well.
Burn Mark
MT Rampart, MT 3rd, ST short
ST Rampart, ST 3rd, ST 40%
Covered by MT Rampart.
The ST gives the MT their short personal mitigations here, because the MT 40% was used to cover Powder Mark Trail.
Burnished Glory #1
MT Reprisal, H1 120, H2 120s, H2 30s, D2
Healer 120s mitigations can be used right after the knockback, and will last to Burnished Glory.
Burnished Glory #2
ST Reprisal, MT 90s, ST 90s, H2 30s, D1, D3, D4
15s mitigations (like Reprisal, Tactician, Heart of Light, etc.) should be applied after the second tether resolves, which will cover the last two tethers in addition to Burnished Glory.
Shields, like Shake It Off and Divine Veil should be saved for Burnished Glory.
Powder Mark Trail #2
PLD > ST Invuln
A PLD MT must Hallowed Ground this Powder Mark Trail for Hallowed Ground to be back in time for P3.
Burn Mark
MT Rampart, MT 40%, MT 30%
ST Rampart, ST 3rd, ST short
The MT gives the ST their short personal mitigations this time, since the ST doesn't have 40% available.
P2. Usurper of Frost
Quad Slap
MT invuln
A PLD cannotHallowed Ground this, or they lose a use over the entire fight (P3 and P5).
Diamond Dust
MT Reprisal, H2 30s, H2 120s, D2, D4
Akh Morn
H1 120s, MT 90s, ST 90s
Hallowed Ray
ST Reprisal, H2 30s, D1
Any "extra" mitigations (Magick Barrier, Passage of Arms, etc.) should be used here.
Light Rampant
MT Reprisal, H2 30s, D2, D4
Mitigations and debuffs that last 15 seconds can cover both the Banish III at the end of Mirror, Mirror and Light Rampant.
House of Light
ST Reprisal, MT 90s, H2 120s
Absolute Zero
MT Reprisal, ST 90s, H1 120s, H2 30s
P3. Oracle of Darkness
Ultimate Relativity
MT Reprisal, H1 120s, H2 120s, D1, D4
The healer 120s are here so that they're back in time for the final Shockwave Pulsar → Memory's End sequence.
Fire/Unholy Darkness #1
Covered by H1 120s and H2 120s from Ultimate Relativity.
Fire/Unholy Darkness #2
MT 90s, ST 90s
Fire/Unholy Darkness #3
D3
Covered by MT 90s and ST 90s from Fire/Unholy Darkness #2.
Shell Crusher → Shockwave Pulsar
ST Reprisal, H2 30s
Black Halo
MT + ST Rampant + 40% + + 3rd + short.
A tank can solo this with full mitigations, but there's no reason to do so.
Darkest Dance
PLD > ST invuln
Shockwave Pulsar
H1 120s, H2 120s
Use 20s mitigations just before the cast resolves to have them cover Memory's End as well.
Memory's End
H2 30s
Covered by H1 120s and H2 120s.
P4. Gaia and Shiva
The main mitigation point here is Crystallize Time. Because the sequence from getting stunned to the knockback is just under 15 seconds, we reserve both healer 120s mitigations for this because they last 20s each and have the largest margin of error.
Darklit Dragonsong
MT Reprisal, MT 90s, ST 90s, D1, D3
Debuffs should target the Usurper of Frost.
Somber Dance
MT invuln
Akh Morn #1
ST Reprisal, H2 30s
MT Rampart, 3rd, short
Morn Afah #1
D2
Covered by ST Reprisal and H2 30s from Akh Morn.
Debuffs should target the Usurper of Frost.
Crystallize Time
MT Reprisal, D4
Debuffs should target the Oracle of Darkness.
Hallowed Wings
MT 90s, ST 90s, H1 120s, H2 120s, D3
MT 40%, ST 40%
15s mitigations should be used right when the Oracle of Darkness does Spirit Taker right before the rewind.
Akh Morn #2
ST Reprisal, H2 30s
ST Rampart, 3rd, short
Morn Afah #2
Covered by ST Reprisal and H2 30s from Akh Morn.
Debuffs should target the Usurper of Frost.
P5. Pandora
Fulgent Blade #1
MT Reprisal, MT 90s, D1
Akh Morn #1
ST Reprisal, ST 90s, D2, D4
Wings Dark and Light #1
MT 40%, Rampart, short, 3rd
ST 40%, Rampart, short, 3rd
Tanks should use their short cds while dodging the Exalines to mitigate the boss's autoattacks. The latest you can use 25s mitigations and have them back for Wings Dark and Light would be around the second Exaline dodge.
Polarising Strikes #1
MT Reprisal, H1 120s, H2 120s, D3
Pandora's Box
Tank LB3
15s mitigations can cover both Pandora's Box and Fulgent Blade if used late enough (around the "B" in "Box").
Fulgent Blade #2
ST Reprisal, MT 90s, D1
Akh Morn #2
MT Reprisal, ST 90s, D2, D4
Wings Dark and Light #2
MT + ST: Invuln
Polarising Strikes #2
ST Reprisal, H1 180s, H2 30s, H2 180s
Fulgent Blade #3
MT 90s, H1 120s, H2 120s
Notably, H2 30s will not be back up in time.
Akh Morn #3
MT Reprisal, ST 90s, H2 30s, D2, D4
Mitigation by Role
MT
P1. Fatebreaker
Cyclonic Break
Reprisal just before the cast bar finishes will last until Powder Mark Trail.
If you are WAR or PLD, you can use Shake It Off/Divine Veil at the start and have it back for Burnished Glory #2.
Powder Mark Trail #1
Reprisal, Rampart, 40%, short
Use Rampart towards the end of the castbar to have it last to the Burn Mark.
Burn Mark #1
Rampart, 3rd
Burnished Glory #1
Reprisal
Burnished Glory #2
MT 90s
If you are a DRK or GNB, you can use Dark Missionary/Heart of Light after the second tether resolves to mitigate the third and fourth tethers in addition to Burnished Glory.
Powder Mark Trail #2 (only if PLD MT)
Hallowed Ground
Burn Mark #2
Rampart, 40%, 3rd
Give short mit to the ST.
P2. Usurper of Frost
Quad Strike
Invuln
Diamond Dust
Reprisal
Sunburst Holy x4
MT 90s
Mirror, Mirror
Rampart, 40%
Cycle through these to mitigate auto-attacks.
Banish III
Reprisal
Use this towards the end of the castbar to also cover Light Rampant.
Give your short mit to D1 during Banish III.
Light Rampant
Reprisal
Absolute Zero
Reprisal
P3. Oracle of Darkness
Ultimate Relativity
Reprisal
Fire/Unholy Darkness #2 or #3
MT 90s
Feel free to use Reprisal anywhere else in this phase before the final Dark Water III stacks at Apocalypse.
P4. Gaia and Shiva
Darklit Dragonsong
Reprisal, MT 90s
Somber Dance
Invuln
Use Rampart when the boss jumps- this will cover Akh Morn #1 and be back for Akh Morn #2 in the event the ST dies.
Akh Morn #1
Rampart, 3rd, short
Crystallize Time
Reprisal
Crystallize Time (Hallowed Wings)
MT 90s, 40%
Use these around the time the Oracle of Darkness jumps on someone (Spirit Taker) just before the rewind resolves.
Akh Morn #2
Give short mit to the ST.
P5. Pandora
Fulgent Blade #1
Reprisal, MT 90s
Wings Dark and Light #1
Rampart, 40%, 3rd, short
Fulgent Blade #2
Reprisal, MT 90s
Wings Dark and Light #2
Invuln
Fulgent Blade #3
Reprisal, MT 90s
ST
P1. Fatebreaker
Burn Mark #1
40%, Rampart, 3rd
Give the MT your targeted short mit.
Burnished Glory #2
ST Reprisal, ST 90s
If you are a DRK or GNB, you can use Dark Missionary/Heart of Light after the second tether resolves to mitigate the third and fourth tethers in addition to Burnished Glory.
Powder Mark Trail #2
Invuln unless you have a PLD MT (in which case, the PLD should take this with Hallowed Ground instead)
Burn Mark #2
Rampart, 3rd, short
P2. Usurper of Frost
Sunburst Holy x4
ST 90s
Absolute Zero
ST 90s
P3. Oracle of Darkness
Fire/Unholy Darkness #2
ST 90s
Shell Crusher → Shockwave Pulsar #1
Reprisal
Memory's End
Reprisal
P4. Gaia and Shiva
Akh Morn → Morn Afah #1
Reprisal
Crystallize Time (Hallowed Wings)
ST 90s, 40%
Use this around the time the Oracle of Darkness jumps on someone (Spirit Taker) just before the rewind resolves.
Of note, the party actually has more than enough mitigation for Hallowed Wings. Consider moving this forward to cover Morn Afah #1 instead.
Akh Morn #2
Rampart, 3rd, short
Reprisal
P5. Pandora
Akh Morn #1
Reprisal, ST 90s
Wings Dark and Light #1
Rampart, 40%, 3rd, short
Fulgent Blade #2
Reprisal
This can also cover Pandora's Box.
Wings Dark and Light #2
Invuln
Polarising Strikes #2
Reprisal
Akh Morn #3
ST 90s
H1
This assumes your H1 is either a WHM or AST. As double barrier healer parties are fairly common, adapt this as needed if H1 is a SCH or SGE.
P1. Fatebreaker
Burnished Glory #1
H1 120s
Use your 120s mitigation early (when the knockback happens just before the boss reappears). You only need to cover the initial damage from Burnished Glory.
Use your 180s abilities early as well, if you want to use them again at Mirror, Mirror.
P2. Usurper of Frost
Sunburst Holy
H1 120s
Absolute Zero
H1 120s
P3. Oracle of Darkness
Ultimate Relativity
H1 120s
This may seem strange, but it's used early here to be back in time for the final Shockwave Pulsar → Memory's End sequence, and should also cover the first set of Dark Fire III.
Shockwave Pulsar #2
H1 120s
Use this a bit before the cast resolves to cover Memory's End as well.
Memory's End
H1 120s
P4. Gaia and Shiva
Crystallize Time
H1 120s
You can use this when the Spell in Waiting: Quietus resolves, and it will still cover the Hallowed Wings.
P5. Pandora
Polarising Strikes #1
H1 120s
Use this no earlier than when the cast bar reaches the "P" in Polarizing Strikes to cover all four hits.
Polarising Strikes #2
H1 180s
Fulgent Blade #3
H1 120s
This cannot cover both Fulgent Blade and Akh Morn.
H2
P1. Fatebreaker
Cyclonic Break
H2 30s
Use this no earlier than when the cast-bar reaches the "C" in Cyclonic Break to also help the MT for Powder Mark Trail.
Burnished Glory #1
H2 30s, H2 120s
Use your 120s mitigation early (when the knockback happens just before the boss reappears). You only need to cover the initial damage from Burnished Glory.
Burnished Glory #2
H2 30s
Use this after the second tether resolves in Fall of Faith to cover the last two tethers and the initial hit from Burnished Glory.
P2. Usurper of Frost
Diamond Dust
H2 30s, H2 120s
Hallowed Ray
H2 30s
Light Rampant
H2 30s
House of Light
H2 120s
Use this early to also cover the Banish III stacks at the end of Light Rampant in addition to House of Light.
Absolute Zero
H2 30s
P3. Oracle of Darkness
Ultimate Relativity
H2 120s
This may seem strange, but it's used early here to be back in time for the final Shockwave Pulsar → Memory's End sequence, and should also cover the first set of Dark Fire III.
Spell in Waiting: Dark Fire III #1
H2 30s
Shockwave Pulsar #1
H2 30s
Apocalypse (Spell in Waiting: Dark Water III #1)
H2 30s
Shockwave Pulsar #2
H2 120s
Use this a bit before the cast resolves to cover Memory's End as well.
Memory's End
H2 30s, H2 120s
P4. Gaia and Shiva
Darklit Dragonsong
H2 30s
Akh Morn → Morn Afah #1
H2 30s
If you use this when the Oracle of Darkness jumps for the second time for Somber Dance, it will cover the four Akh Morn hits, and be back in time for the start of Crystallize Time. However, it will not cover Morn Afah if you do so.
Crystallize Time
H2 30s
Crystallize Time (Hallowed Wings)
H2 120s
You can use this when the Spell in Waiting: Quietus resolves, and it will still cover the Hallowed Wings.
Akh Morn → Morn Afah #2
H2 30s
P5. Pandora
Polarising Strikes #1
H2 120s
Use this no earlier than when the cast bar reaches the "P" in Polarizing Strikes to cover all four hits.
Polarising Strikes #2
H2 180s
Fulgent Blade #3
H2 120s
This cannot cover both Fulgent Blade and Akh Morn.
D1
P1. Fatebreaker
Cyclonic Break
Feint
Use this no earlier than when the cast-bar reaches the "C" in Cyclonic Break to also help the MT for Powder Mark Trail.
Burnished Glory #2
Feint
Use this after the second tether resolves in Fall of Faith to cover the last two tethers and the initial hit from Burnished Glory.
P2. Usurper of Frost
Hallowed Ray
Feint
Absolute Zero
Feint
P3. Oracle of Darkness
Ultimate Relativity
Feint
Critical Error
Feint
P4. Gaia and Shiva
Darklit Dragonsong
Feint
Make sure you Feint the Usurper of Frost.
Akh Morn → Morn Afah #2
Feint
Make sure you Feint the Usurper of Frost.
P5. Pandora
Fulgent Blade #1
Feint
Fulgent Blade #2
Feint
Use this when the castbar reaches the "B" in Pandora's Box to cover Pandora's Box in addition to Fulgent Blade.
Fulgent Blade #3
Feint
D2
This assumes D2 is a melee DPS.
P1. Fatebreaker
Burnished Glory #1
Feint
P2. Usurper of Frost
Diamond Dust
Feint
Light Rampant
Feint
You can use this early to also cover the Banish III stacks at the end of Mirror, Mirror.
P3. Oracle of Darkness
Shell Crusher → Shockwave Pulsar #1
Feint
Memory's End
Feint
P4. Gaia and Shiva
Crystallize Time
Feint
Make sure you Feint the Oracle of Darkness.
P5. Pandora
Akh Morn #1
Feint
Akh Morn #2
Feint
Akh Morn #3
Feint
D3
P1. Fatebreaker
Cyclonic Break
Troubadour/Tactician/Shield Samba
Use this no earlier than when the cast-bar reaches the "C" in Cyclonic Break to also help the MT for Powder Mark Trail.
Burnished Glory #2
Troubadour/Tactician/Shield Samba
Use this after the second tether resolves in Fall of Faith to cover the last two tethers and the initial hit from Burnished Glory.
P2. Usurper of Frost
Sunburst Holy
Troubadour/Tactician/Shield Samba
Use this no earlier than when the star AoE puddles are dropped at the start of Diamond Dust to cover all four Sunburst Holy stacks.
Absolute Zero
Troubadour/Tactician/Shield Samba
P3. Oracle of Darkness
Spell in Waiting: Fire III #2 or #3
Troubadour/Tactician/Shield Samba
P4. Gaia and Shiva
Darklit Dragonsong
Troubadour/Tactician/Shield Samba
Crystallize Time (Hallowed Wings)
Troubadour/Tactician/Shield Samba
Use this around the time the Oracle of Darkness jumps on someone (Spirit Taker) just before the rewind resolves.
P5. Pandora
Polarizing Strikes #1
Troubadour/Tactician/Shield Samba
Polarizing Strikes #2
Troubadour/Tactician/Shield Samba
D4
P1. Fatebreaker
Burnished Glory #1
Addle
P2. Usurper of Frost
Diamond Dust
Addle
Light Rampant
Addle
You can use this early to also cover the Banish III stacks at the end of Mirror, Mirror.